Previously, we summarized the parts of the Democratic and Republican party platforms dealing with issues important to older Americans, including Social Security and Medicare, and what each side would do to promote retirement security – a broader catch-all that includes everything from affordable senior housing to food prices.

But Democratic President Barack Obama and his Republican challenger, former Massachusetts Gov. Mitt Romney, won’t be the only candidates for the nation’s highest office. In many states, third-party candidates from the Libertarian and Green parties also have met qualifications to be on the ballot. They’ll be hoping to appeal to voters’ dissatisfaction with partisan gridlock in Washington – discontent borne out by a recent AARP survey that showed high anxiety levels among boomers, and dismay among 50-plus voters with both Obama’s and Romney’s explanations of what they would do about Social Security, Medicare and retirement security.

What do the alternative parties and their candidates propose to do about those issues? Here’s a rundown:

Libertarian Party: The Libertarians’ candidate, former GOP Gov. Gary Johnson of New Mexico, is on the ballot in 43 states. Libertarians generally support personal autonomy, an unfettered free market, and privatizing most services and benefits now provided by the government. Johnson has pledged to cut $1.4 trillion in federal spending and says bluntly that “you have to start the discussion with Medicare, Social Security and military spending.” The party’s platform criticizes a “failed” Social Security system. Liberarians stop short of calling for the abolition of Social Security, but they want individuals to be able to opt out of the program completely, so they can divert what they would have paid in taxes in private investments. To make up for the loss in revenue needed to fund current retirees’ benefits, Libertarians would auction off the “trillions of dollars” worth of government assets and property that they see as unnecessary to fulfill functions spelled out in the Constitution. Similarly, Libertarians would eliminate Medicare and Medicaid, replacing them with tax-free medical savings accounts that individuals could use to put away money to cover future medical bills. They also pledge to eliminate federal subsidies for housing and the Food Stamp program, both of which help to provide seniors with retirement security. Here’s a Daily Show interview with Johnson.

Green Party: In contrast to the anti-government Libertarians, the Greens want an activist government controlled by ordinary citizens. They aim to fight environmental destruction, create a “sustainable” economic system that guarantees a living wage to all and eliminate discrimination, including ageism. The party’s presidential candidate, Jill Stein, M.D., a Massachusetts internist, is on the ballot in 33 states. Stein said in a 2011 interview that she would protect the solvency of the Social Security system by raising the cap that currently limits Social Security taxes to income below $106,000, though she did not say whether she would eliminate the cap completely. She and the Greens not only want to preserve the current Medicare system but would also expand it to create “Medicare for All,” a national single-payer health care system. They would pay for their plan by cutting military expenditures, raising taxes on the wealthy and adding new taxes on Wall Street transactions and capital gains. On economic issues related to retirement security, Stein said in a 2011 interview that she would create “ample” public housing and have the government take over utility companies to ensure that rates are affordable for all. Here’s an interview with Stein and her running mate, Cheri Honkala, on the satellite and Internet TV program Democracy Now.